﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace DevisionByFiveInARange
{
    class Program
    {
        static void Main(string[] args)
        {
            int startIndex = int.Parse(Console.ReadLine());
            int endIndex = int.Parse(Console.ReadLine());

            int counter = 0;
            for (int index = startIndex; index <= endIndex; index++)
            {
                if (index % 5 == 0)
                {
                    counter++;
                }
            }
            Console.WriteLine(counter);



        }
    }
}
